ASoC: imx: Fix build warning of unused 'card' variable

Fixes the following warning:

  CC      sound/soc/imx/imx-pcm-fiq.o
sound/soc/imx/imx-pcm-fiq.c: In function 'imx_pcm_fiq_new':
sound/soc/imx/imx-pcm-fiq.c:243: warning: unused variable 'card'
  CC      sound/soc/imx/imx-pcm-dma-mx2.o

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>